1,5-AG is present in human cerebrospinal fluid and plasma and it has been reported that its quantity is reduced in plasma with certain diseases, particularly with diabetes. 1,5-AG has been conventionally assayed mainly by gas chromatography (see, e.g., Yoshioka et al., Tonyobyo, 25, 1115-1118 (1982)).
However known methods for assaying 1,5-AG have some disadvantages from the clinical viewpoint such that it is necessary to preliminarily treat a specimen and to label 1,5-AG; that the maintenance of analytical instruments requires troublesome procedures and should be carried out by an experienced person; and that gas chromatographic analysis requires a prolonged period of time, which makes it difficult to assay a number of specimens.
Under these circumstances, we have attempted to develop a method by which a number of specimens can be readily assayed, thus completing the present invention.